Skin And Its Appendages

Skin and Its Appendages

Skin : epidermis,,dermis and its appendages

1. Epidermis 1.1 The stratum of epidermis stratum basale stratum spinosum

epitheliu m

stratum granulosum stratum lucidum stratum corneum

stratum basale

Basal cell ： cuboidal or columnar ， stem cell., basophilic, rich in desmosomes, undifferentiated cell.(germinal layer)

stratum spinosum 4-10-layer prickle cells: polyhedral, basophilic cytoplasm,rich in desmosomes, abundant in keratin filaments.

stratum granulosum 3-5-layer cells: spindle shaped ， with degenerative nuclei and organelles; basophilic,abundant in granules consisting of keratohyalin; more keratin filaments.

stratum lucidum transparent and homogeneous ， without nuclei and organelles, indistinct cell boundaries. similar with cells of stratum corneum

stratum corneum Dead cells: without nuclei and organelles. with disorganized desmosomes. easy to be shed off.

1.2 cells of epidermis

cells

keratinocy te

of epider mis

Melanocyte

unkeratinoc yte

Langerhans cell Merkel cell

melanocyte L/M: lies between basal cells, with thin and long processes which present amongst the cells of the stratum basale and stratum spinosum.

E/M ：① abundant in ribosomes,RER and Golgi complex; ② with membrane bound melanosomes. Function ： protection from the hurt by UV light.

Melanocytes contain melanosomes which contain tyrosinase . Tyrosinase

albinism

tyrosine

melanin

protecti on

absorb UV

Melanocyte

Melani Melani n granul es

Langerhans cell L/M ： lies in the superficial layer of stratum spinosum E/M ： containing characteristic Birbeck bodies which section looks like racket. Function:antigen presenting cell(APC).

Langerhans cell

Langerhans cell

Merkel cell L/M ： lie in stratum basale ， flat cell. E/M ： related to sensory nerve endings. Function ： related to sense

2. dermis papillary layer

dermi s reticular layer

2.1 papillary layer Connective tissue. Abundant in capillaries, free nerve endings and tactile corpuscles.

2.2 reticular layer dense connective tissues, consisting of bundles of collagen fibers, numerous elastic fibers, etc. containing blood vessels, nerve fibers ,lamellar corpuscles, sweat glands ,etc. 。

tactile tactile corpuscle corpuscle

Lamellar Lamellar corpuscle corpuscle

Lamellar Lamellar corpuscle corpuscle

stratum basale stratum spinosum

epider mis

stratum granlosum stratum lucidum

Skin

stratum corneum

dermi s

papillary layer reticular layer

3. appendages of skin

appendages of skin

3.1

hair

Hair shaft 、 hair root 、 hair follicle 、 hair bulb 、 hair papilla 、 arrector pili muscle

shaft shaft hair hair root root hair hair

3.2 sebaceous gland

Localization: between the hair root and arrector pili muscle Function: secreting sebum.

sebaceous gland

sebaceous gland

3.3 sweat gland

Typical sweat glands: mesocrine , apocrine holocrine Function: secreting sweat. regulating body temperature and related to metabolism. Atypical sweat glands: apocrine the secretions are viscous, odourless, and contain proteins

Sweat gland

Key points 1) constitution of the skin:epidermis,dermis and its appendages. 2) 5 layers of the epidermis, the cell constituents of the epidermis(keratinocyte and unkeratinocyte) 3) 3 types of the unkeratinocyte and their functions. 4) 2 kinds of sweat glands and their secretions.